The aim of this research is to use the Harvester ant (Pogonomyrmex barbatus) as a model system to study one of the central questions concerning the integration of complex biological systems, i.e. how do individuals process local information and alter behavior in response? I propose to study the molecular basis of task allocation in Harvester ant colonies by assaying gene expression in workers of different tasks. Task behaviors of this species are well documented and relatively labile. Task switching is mediated by environmental cues such increased food resources, or by social cues, i.e. changes in interaction rate with nestmates. I will test the hypothesis that the differences in task behavior involve differential expression of genes, particularly genes required for chemosensory processing. The goal of this research is to develop custom cDNA microarrays enriched for genes expressed in Harvester ant workers exhibiting two task behaviors, foraging and midden work, as well as transcipts for chemosensory processing genes identified in other insects. Target genes associated with each task behavior will be sequenced and identified, if possible. Using stimuli known to induce resting worker ants to switch to a particular task, I will test whether target genes for foraging or midden work are expressed in task-switching ants. This research will add to our understanding of the mechanisms of behavioral control in complex systems by determining fundamental genetic factors involved in task behaviors of this species.